1. Field of the Invention
The invention is based on a method for the operation of a power plant in accordance with the preamble of the independent claim.
2. Discussion of Background
Power plant installations which burn carbon-containing fuels as compressed atmospheric air is supplied are generally known. However, the combustion gases produced during the combustion, such as carbon dioxide (CO2) and nitrogen oxides, present a multilayered problem and, not least, are implicated in global warming.
EP 0 953 748 A1 has disclosed a power plant with a closed or quasi-closed cycle. The cycle is operated with a CO2-containing medium with internal combustion of a fuel and the oxygen required for this purpose. Excess CO2 is removed from the cycle and introduced into a condensation installation, and the condensed CO2 can then be disposed of in an environmentally friendly way. The use of a closed or quasi-closed cycle with the addition of pure oxygen moreover prevents atmospheric nitrogen from entering the flame, and consequently no nitrogen oxides, or at most only low levels of nitrogen oxides, are formed.
However, the design of the cycle means that inert gases which are entrained with the fuel or oxygen accumulate in the process to well above the starting concentration and, as a result of a shift in the thermodynamic properties of the working medium, may have a considerable adverse effect on the process efficiency. The composition of the fuel used cannot be influenced by the process described, but the oxygen fed to the process should be as pure as possible, in order to minimize the levels of inert gases.
Hitherto, it has only been possible to produce high-purity oxygen in the quantities required by cryogenic means. In this context, the high costs of the air fractionation installation, which places a question mark over economic operation of power plants with a closed or quasi-closed cycle, are mainly caused by the low concentration of oxygen in the ambient air and the resulting large mass and volumetric flows which are required in the air fractionation installation.